This invention relates to a magnetic tape cartridge comprising a cartridge casing and a single reel which is housed in the cartridge casing for rotation and around which a magnetic tape is wound.
As a recording medium for use as a backup for a computer memory, there has been known a magnetic tape cartridge comprising a magnetic tape wound around a single reel and a flat cartridge casing which is formed of square upper and lower casing halves fastened together and in which the reel is housed for rotation.
Since the magnetic tape is used for storing important information, the magnetic tape cartridge is structured so that trouble such as tape jam does not occur and the magnetic tape is not accidentally drawn out.
A leader member (e.g., a leader pin) is fixed to the leading end of the magnetic tape and the recording and reproducing apparatus is arranged to catch the leader member to draw out the magnetic tape from the magnetic tape cartridge to a position where information recorded on the tape can be read out and information can be recorded on the tape. The leader pin is removably held on the cartridge casing. It is advantageous for the purpose of simplification of the structure to hold the leader on the cartridge casing by use of a spring member.
When a leader pin is employed as the leader member, the leader pin generally comprises a central shaft portion to which the leading end portion of the magnetic tape is fixed, a pair of thin shaft portions formed on opposite ends of the central shaft portion, and a pair of head portions which formed on outer sides of the thin shaft portions and is of substantially the same diameter as the central shaft portion. The thin shaft portions form engagement portions which are brought into engagement with a tape draw-out mechanism of a recording and reproducing apparatus when the magnetic tape cartridge is loaded in the recording and reproducing apparatus. The head portions on opposite ends of the leader pin are brought into engagement with leader pin holding recesses formed in the upper and lower casing halves inside the tape draw-out opening. A spring member formed of a plate spring or the like resiliently abuts against the outer peripheral surfaces of the head portions sideway and removably holds the leader pin in the leader pin holding recesses with the axial direction of the leader pin directed in the vertical direction.
The tape draw-out mechanism of the recording and reproducing apparatus is arranged on the assumption that the lower end of the leader pin is located at a predetermined distance from the lower surface of the magnetic tape cartridge, i.e., the bottom surface of the lower casing half of the cartridge casing. That is, it necessary that the leader pin received in the cartridge casing should be constantly held in place in the axial direction thereof.
However, to nullify clearances above and below the leader pin in the leader pin receiving portion is impossible due to limitation in processing accuracy and/or assembling accuracy of the cartridge casing, and is very difficult due to limitation in accuracy of the recording and reproducing apparatus. Accordingly, there exist clearances above and below the leader pin in the cartridge casing, and the leader pin can be displaced from the correct position in its axial direction due to inaccuracy when the leader pin is inserted, and/or to drop impact or vibration during transportation or handling of the magnetic tape cartridge.
In order to overcome these problems, a first object of the present invention is to provide a leader pin locating structure which can confine downward the leader pin held in the cartridge casing.
When the leader pin is taken out from the cartridge casing by the tape draw-out mechanism of the recording and reproducing apparatus, and when the leader pin is returned to the cartridge casing by the tape draw-out mechanism, a part of the spring member is deformed in response to movement of the leader pin. Especially when the spring member is of a plate spring, the edge of the deformed part can scratch the inner surface of the cartridge casing to increase frictional resistance. The increased frictional resistance changes load on the spring member and makes instable the action of the spring member. At the worst, the spring member can be caught by the inner surface of the cartridge casing, and the leader pin can be disabled from being taken out from and received in the cartridge casing.
Further, when the edge of the spring member of metal scratches the inner surface of the casing every time the leader pin is taken in and out the cartridge casing by the tape draw-out mechanism of the recording and reproducing apparatus, the inner surface of the cartridge casing is scraped and shavings can adhere to the surface of the magnetic tape to cause drop out.
Thus a second object of the present invention is to provide a spring member mounting structure which can stabilize the action of the spring member for holding the end portion of the leader pin and can prevents the inner surface of the cartridge casing from being scraped.
Further, the spring member for holding the end portion of the leader pin is required to be simple in structure, to be able to surely hold the leader pin and to be able to be easily incorporated in the cartridge casing.
Accordingly, a third object of the present invention is to provide a spring member which meets such requirements.
The leader pin is required to be simple in structure, to be able to surely and easily clamp the leading end portion of the magnetic tape, and keeps strong clamping force irrespective of environment.
Accordingly, a fourth object of the present invention is to provide a leader pin which can meet such requirements and is provided with a which is less in creep and stress relaxation.
When the leader pin is provided with a clamp member of synthetic resin, injection molding, which can form products of a complicated shape at high efficiency with a high dimensional accuracy, is very useful. However, the injection molding is disadvantageous in that a gate mark projects beyond the surface of the product, which causes a problem in dimensional accuracy.
Thus a fifth object of the present invention is to provide a leader pin having a clamp member whose gate mark is positioned not to adversely affect function of the leader pin.
In order to accomplish the first object, a first aspect of the present invention provides a magnetic tape cartridge characterized in that an inclined surface directed obliquely downward is formed at least a part of the side wall of the recess formed in the upper casing half opposed to the direction in which the spring member urges the leader pin. The inclined surface maybe curved. An inclined surface may be additionally provided in a side wall of the inlet portion of the recess in the upper casing half.
By providing such an inclined surface, the leader pin is constantly urged downward by the force of the spring member, whereby the leader pin is prevented from being moved upward by drop impact and/or vibration during transportation, and the leader pin can be kept on a level conforming to the tape draw-out mechanism of the recording and reproducing apparatus. Further, when an inclined surface is additionally provided in a side wall of the inlet portion of the recess in the upper casing half, the leader pin can be confined downward under counterforce to the leader pin insertion force of the member of the recording and reproducing apparatus.
Further, in order to accomplish the first object, a second aspect of the present invention provides a magnetic tape cartridge characterized in that a guide surface inclined downward in the direction of insertion of the leader pin into the recess in the upper casing half is provided on the lower surface of the top wall of the upper casing half at the inlet portion of the recess.
The guide surface may extend from the edge of the tape draw-out opening deep to the interior of the recess or from the edge of the tape draw-out opening to a position near the center of the upper head portion of the leader pin. Otherwise, the guide surface may extend from the edge of the tape draw-out opening to the upper head portion of the leader pin.
By providing such a guide surface, the leader pin can be confined downward when the leader pin is inserted into the recess by the member of the recording and reproducing apparatus.
In order to accomplish the first object of the present invention, a third aspect of the present invention provides a magnetic tape cartridge characterized in that the urging force of the spring member applied to the head portion of the leader pin has a component which urges downward the leader pin.
In this case, the head portion of the leader pin may be provided with an inclined surface facing obliquely upward so that the force of the spring member acting on the inclined surface generates the component which urges downward the leader pin. By the component which urges downward the leader pin, the leader pin can be confined downward.
In order to accomplish the first object of the present invention, a fourth aspect of the present invention provides a magnetic tape cartridge characterized in that a recess or a cutaway portion is provided in the head portion of the leader pin and an engagement portion adapted to be engaged with the recess or the cutaway portion if provided on the spring member. With this arrangement, the leader pin can be confined downward by the spring member.
In this case, the recess or the cutaway portion may be in the form of a groove formed in the outer peripheral surface of the head portion. Further, the recess or the cutaway portion may be in the form of a step formed by cutting an upper portion of the outer peripheral surface of the head portion of the leader pin so that an engagement portion of the spring member engaged with the step urges the leader pin also downward. Further, in this case, it is preferred that the lower surface of the engagement portion of the spring member be inclined in the direction of insertion of the leader pin so that the downward urging force is increased as the leader pin is inserted deep into the tape draw-out opening.
In order to accomplish the first object of the present invention, a fifth aspect of the present invention provides a magnetic tape cartridge characterized in that at least the lower head portion of the leader pin is formed of a magnetic material and a permanent magnet is embedded in the lower casing half of the cartridge casing in a place with which the lower head portion of the leader pin is brought into contact.
In order to accomplish the first object of the present invention, a sixth aspect of the present invention provides a magnetic tape cartridge characterized in that a ball plunger which presses downward the leader pin is embedded in the upper casing half of the cartridge casing at a portion opposed to the upper head portion of the leader pin. With these arrangement, the leader pin can be confined downward.
Further, in order to accomplish the first object of the present invention, a seventh aspect of the present invention provides a magnetic tape cartridge characterized in that a second urging means for urging downward the leader pin is provided on the upper casing half of the cartridge casing, and the maximum load point on the leader pin by the first urging means and that by the second urging means are displaced from each other in the direction of insertion of the leader pin. With this arrangement, the leader pin can be confined downward under the urging force of the second urging means. At the same time, since the maximum load point on the leader pin by the first urging means and that by the second urging means are displaced from each other in the direction of insertion of the leader pin, the leader pin can be prevented from being inserted and held in an inclined state due to imbalance of transverse urging forces acting on the leader pin at its upper portion and lower portion.
Further, in order to accomplish the first object of the present invention, an eighth aspect of the present invention provides a magnetic tape cartridge characterized in that the slide door is provided on the back side thereof with a rib having an inclined surface which is brought into abutment against the upper surface of the head portion of the leader pin and presses downward the leader pin in response to movement of the slide door to the closing position. Also with this arrangement, the leader pin can be confined downward.
In order to accomplish the second object of the present invention, a ninth aspect of the present invention provides a magnetic tape cartridge characterized in that the spring member comprises a base portion which is mounted on the inner surface of the upper or lower casing half of the cartridge casing and an arm portion which extends from the base portion and can be deflected to removably hold the upper or lower end portion of the leader pin, and the edge of the arm portion opposed to the inner surface of the cartridge casing is provided with a cutaway portion for preventing the arm portion from being brought into contact with the inner surface of the cartridge casing.
With this arrangement, action of the spring member is stabilized and the problem that the inner surface of the cartridge casing is scraped can be overcome.
In this case, it is preferred that the spring member is a single member comprising a base portion and upper and lower arm portions extending from upper and lower portions of the base portion.
In order to accomplish the second object of the present invention, a tenth aspect of the present invention provides a magnetic tape cartridge characterized in that the spring member comprises a base portion which is mounted on the inner surface of the upper or lower casing half of the cartridge casing and an arm portion which extends from the base portion and can be deflected to removably hold the upper or lower end portion of the leader pin, and the inner surface of the cartridge casing opposed to the arm portion is recessed with respect to the inner surface of the cartridge casing opposed to the base portion. Also with this arrangement, the arm portion can be prevented from being brought into contact with the inner surface of the cartridge casing when it is deflected.
In order to accomplish the third object of the present invention, an eleventh aspect of the present invention provides a magnetic tape cartridge characterized in that the spring member is a single member comprising a base portion and upper and lower arm portions which extend from upper and lower portions of the base portion and can be deflected to removably hold the upper or lower end portion of the leader pin.
When the spring member is of this arrangement, the spring member can be incorporated in the cartridge casing by fastening together the upper and lower casing halves, and accordingly, incorporation of the spring member is facilitated and the number of parts is reduced, whereby cost can be reduced.
In this case, it is preferred that the spring member be provided with upper and lower arm portions for incorporation in addition to the upper and lower arm portions for holding the leader pin, with the upper and lower arm portions for incorporation being symmetrical with the upper and lower arm portions for holding the leader pin so that the spring member is symmetrical about both its horizontal and vertical axes, whereby the spring member becomes nondirectional and incorporation of the spring member in the cartridge casing is further facilitated.
In this case, it is preferred that cutaway portions into which the arm portions for incorporation are inserted be formed in the inner surface of the cartridge casing.
When the spring member is a single member comprising a base portion and upper and lower arm portions which extend from upper and lower portions of the base portion and can be deflected to removably hold the upper or lower end portion of the leader pin, it is preferred that the spring member be further provided with a pressing piece which presses downward the leader pin in the axial direction of the leader pin.
Further, when the spring member is a single member comprising a base portion and upper and lower arm portions which extend from upper and lower portions of the base portion and can be deflected to removably hold the upper or lower end portion of the leader pin, it is preferred that the spring member be formed by bending opposite end portions of a line spring like a hairpin so that the opposite end portions form the upper and lower arm portions and the middle portion forms the base portion.
In this case, the spring member can be fixed to the cartridge casing by bending an intermediate portion of the base portion to form a mounting portion, forming in each of the upper and lower casing halves a spring member mounting groove which opens the mating surface of the casing half, and mating the upper and lower casing halves so that the respective mating surfaces are opposed to each other with a part of the mounting portion of the spring member received in the spring member mounting groove of one of the upper and lower casing half and the other part of the mounting portion received in the spring member mounting groove of the other of the upper and lower casing halves.
In order to accomplish the second and third objects of the present invention, a twelfth aspect of the present invention provides a magnetic tape cartridge characterized in that the spring member comprises a pair of line springs each of which is provided with an arm portion which is deflected to removably hold an end portion of the leader pin, and a cutaway portion for preventing the arm portion from being brought into contact with the inner surface of the cartridge casing when the arm portion is deflected is formed in the arm portion of at least one of the line springs.
In order to accomplish the third object of the present invention, a thirteenth aspect of the present invention provides a magnetic tape cartridge characterized in that the spring member comprises a pair of line springs each of which comprises a pair of arm portions extending substantially in parallel to each other from a bight portion, one of the arm portions being arranged to removably hold an end portion of the leader pin and the other arm portion being used for incorporating the spring member in the cartridge casing, the inner diameter of the bight portion being substantially equal to the outer diameter of a support pin and a retainer portion in the form of a projection being formed on the inner side of a portion between the bight portion and the arm portion for incorporating the spring member in the cartridge casing.
In order to accomplish the fourth object of the present invention, a fourteenth aspect of the present invention provides a magnetic tape cartridge comprising a cartridge casing, and a single reel around which a magnetic tape with a leader pin fixed to the leading end thereof is wound and which is contained in the cartridge casing for rotation,
wherein the improvement comprises that the leader pin comprises a pin body with a central shaft portion, and a clamp member which is formed by synthetic resin, is provided with an axial slit to be C-shaped in cross-section, and is resiliently press-fitted on the central shaft portion through the slit with the leading end portion of the magnetic tape pinched between the inner wall surface of the clamp and the outer surface of the central shaft portion, whereby the leading end portion of the magnetic tape is fixed to the leader pin.
It is preferred that a chamfered portion be formed along the inner peripheral surface of the end face of the clamp member so that the chamfered portion acts as a guide surface which guide the clamp member when it is press-fitted on the central shaft portion.
It is preferred that the clamp member be formed of synthetic resin which is 130xc2x0 C. or higher in deflection temperature under load.
Otherwise it is preferred that the clamp member be formed of synthetic resin which is 220xc2x0 C. or higher in melting temperature or softening temperature.
When the clamp member is formed of synthetic resin, the clamp member is normally under stress in the direction in which the clamp member is press-fitted on the central shaft portion. Accordingly, there is a problem that when the magnetic tape cartridge is stored or used at an elevated temperature or in a high-temperature high-humidity atmosphere, the tape clamping force deteriorates due to creep (permanent deformation generated when subjected to constant stress within limit of elasticity for a long time) and stress relaxation (a phenomenon that the stress necessary to generate predetermined strain is gradually reduced with time). When the clamp member is formed of synthetic resin which is 130xc2x0 C. or higher in deflection temperature under load or synthetic resin which 220xc2x0 C. or higher in melting temperature or softening temperature, the problem that the tape clamping force deteriorates when the magnetic tape cartridge is stored or used at an elevated temperature or in a high-temperature high-humidity atmosphere can be overcome.
It is preferred that the clamp member be formed of synthetic resin reinforced with glass fiber or the like.
The synthetic resin reinforced with such fiber is higher in deflection temperature under load than resin not reinforced. Accordingly, even synthetic resin which is lower than 130xc2x0 C. in deflection temperature under load by itself can be used for forming the clamp member by reinforcing with fiber.
In order to accomplish the fifth object of the present invention, a fifteenth aspect of the present invention provides a magnetic tape cartridge comprising a cartridge casing, and a single reel around which a magnetic tape with a leader pin fixed to the leading end thereof is wound and which is contained in the cartridge casing for rotation,
wherein the improvement comprises that the leader pin comprises a pin body with a central shaft portion, and a clamp member which is formed by synthetic resin, is provided with an axial slit to be C-shaped in cross-section and is resiliently press-fitted on the central shaft portion through the slit with the leading end portion of the magnetic tape pinched between the inner wall surface of the clamp and the outer surface of the central shaft portion, whereby the leading end portion of the magnetic tape is fixed to the leader pin, and a recess is formed on at least one of the end faces with a gate mark formed in the recess.
Otherwise, an end face of the clamp member is obliquely cut on opposite sides of the slit to form an inclined guide surface, and a gate mark is formed on the inclined guide surface.
The outer surface of the clamp member opposite to the slit may be cut partly or over the entire length of the clamp member to form a flat surface and the gate mark may be formed on the flat surface.
The inner surface of the clamp member may be thinned over the entire periphery at least at a part adjacent to one end face to form a recess on the inner surface and the gate mark may be formed on the recess.
The inner surface of the clamp member may be partly thinned to form a recess extending in the axial direction of the clamp member and the gate mark may be formed on the recess.
When the gate mark is formed in sites described above, the gate mark cannot project beyond the basis contour of the clamp member. Accordingly, the aforesaid problems of unsatisfactory press-fitting of the clamp member on the central shaft portion of the leader pin, deterioration in positional accuracy, damage of the magnetic tape or interference of the leader pin with a component of the tape drive apparatus can be overcome and function of the leader pin can be ensured.